Engine management light MAP sensor

[Fabiafail]

Hi All, I'm new to the forum, but I've read a few threads and the info is great! 

My problem is with my girlfriends fabia 1.4MPI (2002). It was running a bit rough, so i decided to change the plugs, clean the throttle body and MAP sensor. Since then it has been throwing up  a P0101 fault. It's been ongoing for the past 2 weeks.                Since it started I have changed the MAP sensor twice (2 different new sensors. First one i took back because it wasn't OEM). Removed the throttle body and resealed the mating face to the manifold. Checked all the hoses for splits/ cracks. All to no avail. what is even more suspicious is that the other day she started the car and the engine management light had gone out, it had somehow reset the fault itself (shouldn't do that!) Of course after a day it came back on :-( 

         I was wondering where to go now? I have a couple of idea's , but would like to know if there is anything common that could be causing the problem?

My idea's are:

1) wiring to the MAP, i checked the pins in the connector and they are bright and clean.

2) Possible vacuum leak at the injectors, I started to remove them to clean them, but decided against it and refitted them before they were fully removed.

3) vacuum leak before the throttle body. the seal on the plastic duct that fits onto the throttle body does not seem to be a tight fit.

4) Fault with the instrument cluster itself. Before this all started she had an immobiliser fault (car wouldn't start) I disconnected the cluster and battery to check for damaged cables etc (found nothing obvious). When i reconnected everything the car was fine. Started without faults and has not had an immobiliser fault since (4 weeks now)

5) bad connection / earth fault with the ECU

 

In addition to this the ESP/TCS light is on almost constantly (solid light, not flashing), but the ABS light is not on.

 

TBH i'm a bit fed up with this car and struggling to get my head round it, so any advice would be great.

 

thanks in advance :-) 

 

[waool1988]

Ok!!  ..  I am trying to connect the dots here and I think you have a vacuum leak for two reasons:

1) The fault code is related to the MAF/MAP sensor which means either there is something wrong with it or its reading does not make any sense.

2) The ESP/TCS light is on because you don't have enough vacuum in the inlet manifold.

 

I would advise you to look at all the vacuum hoses between the engine head and the throttle body/Inlet manifold. Moreover, check on the hose between the vapor fuel valve and the throttle body.

[Fabiafail]

Hi waool1988, 

             First off, Thanks for the prompt response :-). Secondly, sorry for such a long winded posting. I just wanted to give as much info as I could remember.

             I will check all the vacuum hoses again. There is a small non return valve on the throttle body. the hose from it goes to the rocker cover. is it possible that this could cause the fault if it fails?

 

thanks again..

[waool1988]

Yes, check these out. When I bought my car they were worn out completely and I replaced all of them.

 

Don't worry about how long your post is because you did the right thing by giving as much info as possible and your welcome  ...  I hope you would sort it out soon

[Fabiafail]

Hi Again,

 

Finally got the chance to check all the hoses on the inlet manifold and the throttle body. They are all in reasonably good condition. I have removed them, inspected them and refitted them. I put some high vacuum grease on all the nipples before refitting the hoses, to ensure a good seal. All to no avail, both the engine management light and the TCS/ESP light have returned after a short run.

 

Can anyone advise further?

 

Thanks in advance...

[waool1988]

Is it running rough around ideal?

[ajs_vrs]

O2 sensor?

[Fabiafail]

Hi there,

 

Yes it is running rough at idle, more than usual for this tractor engine.

 

It's not showing any fault code for the O2 sensor.

 

I was wondering if It needs a throttle body alignment via VCDS, since I've had the plug off the throttle body?

[sepulchrave]

I was wondering if It needs a throttle body alignment via VCDS, since I've had the plug off the throttle body?

 

Yes.

[Fabiafail]

Cheers  ,

 

will get the throttle body alignment done and let you all know how it goes.

[waool1988]

I still think it is a vacuum leak  ...  Are you sue u installed the throttle body properly?

[ajs_vrs]

Can you monitor fuel trims?

[Fabiafail]

Hi ajs_vrs,

 

I don't have VCDS to monitor. It's gonna have to got to the garage to get the TBA done :(

[waool1988]

Ok  ...   How about letting the car re-calibrate itself?

 

1) Disconnect the battery for 20m

2) Connect the battery

3) Start up the car and leave it to idea for 10m without touching the steering wheel, the accelerator pedal, or the A/C - heater

[Fabiafail]

Nice one, I will give that a try tonight and let you know.

 

Cheers

[Fabiafail]

:'(  Letting it re-calibrate itself didn't work. gonna have to get a local VAG specialist do the TBA and take it from there. Suspicious, that there is still a vacuum leak somewhere, but damned if I can find it 

[Fabiafail]

Right, think I may be getting somewhere.. without a doubt it's a vacuum issue. 

1) I've removed all the hoses and throttle body (left the plug connected). 

2) Blew and sucked through all the vacuum hoses, they seem to sustain the vacuum created by sucking and the non returns work as they should.

3) taped up all the hoses with insulating tape (just to be sure & as a temporary measure)

4) put high vacuum grease on all the nipples to ensure a good seal with the hoses.

5) cleaned the mating faces of the throttle body and manifold and rebuilt using gasket and hylomar(PL32).

finished rebuilding and started the car. no fault light showing (no EML or TCS/ESP lights). After a few minutes the lights came back on.

 

I decided to test the brake servo.

1) switched off the engine and pumped the pedal a few times

2) kept the pressure on the brake pedal and started the engine.

3) brake pedal dropped a couple of inches (as it should with the vacuum assist)

4) did this a couple of times to double, triple check

5) after a few times i left my foot on the brake pedal, turned the engine off and on again.

6) after the second time doing this, keeping my foot on the pedal (applying pressure all the time), both the EML and the TCS light went out.

7) the TCS light came back on after about 20-25 seconds.

8) I repeated this about 10 times to check its concistency. Everytime the results were the same.

9) I also found if I did steps 5 and 6, then took my foot off the pedal straight away, the TCS light came on after only 4-6 seconds.

 

The only difference I can think of is the volume of air. In step 7, because the pedal is depressed there is a smaller amount of space on the vacuum side of the diaphragm so the total size of the vacuum circuit is smaller. whereas in step 9 the pedal is release, the diaphragm moves back and the volume increases, causing a faster collapse of the vacuum in the circuit.

 

having eliminated all the usual suspects, I am drawn to conclude that the diaphragm in the brake servo may have a split in it.

 

I've had enough, the car will be going to a garage to get vacuum checks carried out. initially on the brake servo and then on the other components.

 

If anyone has any comments, feel free.

i'm open to all/any suggestions

cheers

and thanks for listening to my constant bleating

[Fabiafail]

Had the throttle body adaptation done yesterday at a local VAG indie. Hasn't made a difference! spoke to the chap that did it and he told me that you don't really need to do a TBA unless you disconnect the throttle body electrics and turn the ignition on. If you simply disconnect it for cleaning and refitted & connect it, then the ECU retains the original settings. The symptom of the TBA needing done is erratic running, cutting out and poor/ incorrect throttle response when the accelerator pedal is pressed. 

I had him do the TBA anyway and got him to run a diagnostics. Faults showing are:  Running too lean and air mass/ MAP sensor out of range. Deffo a vacuum leak.

Gonna have to strip the whole inlet manifold and replace all gaskets/seals :-( 

I might try making a smoke machine to see it it draws in anywhere.

improvised smoke machine consists of: a jam jar with a hole cut in the lid to take a pneumatic bulkhead fitting, some 4mm pneumatic hose and some smoke pellets.

I will let you know how I get on

cheers

[mrdaf]

How did you get on?

 

May I ask where you aquired your throttle body gasket from?

 

Thanks.

[Fabiafail]

Hi All,

 

Got it sorted!! Yee Haa! It was the inlet manifold gasket! At some point in it's previous ownership, someone had the manifold off and not tightened up the bolts/nuts correctly. Overtime the gasket had started do disintegrate. Resulting in the engine drawing air through the gasket. Quite an easy strip on the 8v 1.4. It only took about 1Hr, including cleaning all the mating faces and rebuilding. The gaskets cost £8 from ebay:

 

http://www.ebay.co.uk/itm/321192085535?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

 

The home made smoke machine was a bit hit and miss. I had to add a second pipe, so i could blow air into the jar and force the smoke out. But the 4mm hose I used for the blow pipe was too small. Larger hose for the blow side is needed and a better seal on the jar lid.

 

In the end I just bit the bullet and stripped the manifold off to visually check the gaskets and lucky for me they were obviously gubbed.

 

Hi MrDaf, I made the throttle body gasket myself. I had some good quality gasket paper it my garage. Used the old one as a template and spent the better part of 3/4 of an hour cutting it out (carefully) with a stanley knife. the original gasket is very thin and there wasn't much compression on it, so I wasn't convinced that it would create an effective seal.

 

Thanks to everyone who offered advice.

 

Cheers

Fabiafail.